code: def test_poisson():
      data = camera()  # 512x512 grayscale uint8
      rng = np.random.default_rng(42)
  
      cam_noisy = random_noise(data, mode="poisson", rng=42)
      cam_noisy2 = random_noise(
          data, mode="poisson", rng=42, clip=False
      )
  
      expected = rng.poisson(img_as_float(data) * 256) / 256.0
      assert_allclose(cam_noisy, np.clip(expected, 0.0, 1.0))
      assert_allclose(cam_noisy2, expected)
  
file_path: scikit-image/skimage/util/tests/test_random_noise.py
imports: from skimage._shared import testing
  from skimage._shared.testing import assert_array_equal, assert_allclose
  import numpy
  from skimage.data import camera
  from skimage.util import random_noise, img_as_float
label_desc: Use image node_id 10 for calling a global function with example usage: test_poisson() without return types